1. Field of the Invention
The present invention relates to an optical device for electrically controlling retrieval of light in a light guide and a display apparatus using the optical device. The present invention further relates to a thin-structured, lightweight and large-screen display apparatus which is capable of preventing degradation of image and providing high-contrast display.
2. Description of the Prior Art
Recently, in research and development of a flat panel display to be display means of image information, demand is increasing for a large-area display apparatus which is ready for set-up and transportation. As prior art display apparatus, for example, a plasma display, a liquid-crystal display, and the like are known.
The plasma display is a display utilizing a light emission phenomenon in association with gas discharge, which is at present limited to about 50 inches in screen size. Further, since problems such as in weight, cost, productivity and the like occur with increasing screen size, there are still problems to be solved in general application as a large-screen display apparatus.
As to the liquid-crystal display, since its tin film transistor(TFT) drive board as a main component makes use of an advanced and fine semiconductor process, it is difficult to be large-sized. Further, the liquid-crystal display is driven from an end of the panel, there occurs a substantive problem of delaying signal propagation time in association with increasing screen size, that is, in construction of a large-area screen.
Further, there is known a projector using a liquid-crystal light bulb. An example thereof is shown in FIGS. 1A and 1B. FIG. 1A is a schematic sectional diagram showing a projector as a display apparatus using a liquid-crystal light bulb as an example of a prior art display apparatus, and FIG. 1B is a schematic sectional diagram showing the construction of the liquid-light bulb applied to the display apparatus.
The projector is constructed by arranging the light bulbs in an array to from a liquid crystal panel 10, illuminating the liquid-crystal panel 10 driven by a matrix electrode from the backside by an illumination 11, and focusing on a screen 13 by a lens 12.
Incident light from a light source(i.e., illumination 11) to the liquid-crystal panel 10 is linearly polarized by a polarizing plate 14, and applied to a twisted nematic(TN) liquid crystal cell 15.
When no electric field is applied to the liquid-crystal cell 15, the polarization direction is rotated by 90 degrees, but when applied with an electric field, the polarization direction is unchanged, and the light transmits, as is. Therefore, by selecting a polarization in a specific direction by a polarizing plate 16, light transmission or blocking can be electrically selected, thus providing a light bulb.
However, the projector of such a construction requires a depth for illuminating from the backside, which inevitably results in a large-sized apparatus.
As an alternative to the above-described plasma display, liquid-crystal display, and projector, the present invention proposes a display apparatus capable of providing a large screen, which uses a light guide and a liquid crystal. In this display apparatus, using a lightweight and inexpensive material as the light guide, and light propagating in the light guide can be retrieved to achieve a large-area screen which is lightweight, inexpensive, and thin-structured.
Here, as an example of prior art display apparatus using a light guide and a liquid crystal, a display apparatus disclosed in Japanese Patent Application Laying-open No. 6-308543(1994) will be described with reference to FIG. 2. This display apparatus comprises a light guide 21 having on the side surface thereof a light source 22 and a reflecting plate 23 for the light source, an electrode 25a provided on the lower surface of the light guide 21 through an electrode support substrate 26a, a ferroelectric liquid-crystal layer 24 provided on the lower surface of the electrode, an electrode 25b provided on the lower surface of the liquid-crystal layer 24, and a reflecting plate 27 provided under the electrode 25b through an electrode support substrate 26b. In this case, furthermore, a light-diffusing plate 28 is provided on the light guide 21.
With this construction, by light scattering of a disclination line appearing when applied with an AC electrical field in the vicinity of relaxation frequency of Goldstone mode of the liquid crystal, output light from the upper surface of the light guide can be adjusted to display an image. However, in the above invention, differing from a TN crystal or the like, application of an electric field by AC drive is essential. For this reason, there has been a disadvantage that passive matrix drive and active matrix drive such as TFT drive are difficult and bit-map display cannot be performed. Further, since directivity of scattering cannot be controlled, light intensity in the display direction (in general, normal direction to the display surface) is not enhanced. Still further, the invention does not describe ease of fabrication in large-screen construction nor signal delay.
Yet further, as examples of other prior art display apparatus, there are known display apparatuses disclosed in Japanese Patent Application Laying-open No. 6-347790(1994), U.S. Pat. No. 4,626,074, Japanese Patent Application Laying-open No. 6-258640(1994)(U.S. Pat. No. 5,452,385) and the like.
Specifically, in the display apparatus disclosed in Japanese Patent Application Laying-open No. 634779(1994), light is guided in a display part and scattering and transmission state of the display part is controlled to make display, in which the display part uses a phase transition-type liquid crystal (not described in detail) or a conventional polymer dispersed liquid crystal. Here, the conventional polymer dispersed liquid crystal becomes a scattering state when no electric field is applied, and a transmission state when an electric field is applied. Since the conventional polymer dispersed liquid crystal has no directivity in its scattering state, light intensity in the display direction cannot be enhanced. Further, in its transmission state, it has a high transmissivity when viewed from the front direction, however, scattering is high when viewed from a small angle with respect to the display surface. Similarly, contrast is low when viewed from the side surface, as a result, scattering state and transmission state may reverse. Still further, when matrix drive is performed, since the spacing between electrodes always shows scattering, display of black is difficult, resulting in a very low contrast display screen. In the specification of the above invention, any of ease of fabrication of large-area construction and signal delay is not described.
The specification of U.S. Pat. No. 4,626,074 discloses a display screen using light scattering by liquid-crystal layer. However, in this case, since diffraction is not used, the output direction cannot be controlled. Still further, in the display apparatus according to the invention, a gap is required on the backside surface, and problems of divisional drive in the large-area construction, ease of fabrication, signal delay and the like are still unsolved, which makes it difficult to achieve a large-area construction.
Since any of the above-described technologies on prior art display apparatus controls display by scattering and transmission, the display screen is illuminated by an illumination at the side of a person looking the display apparatus. As a result, scattered light overlaps with the display image, the display image is affected not only by the color of the light source but also by ambient illumination light, which degrades the display image and makes color display difficult.
Yet further, Japanese Patent Application Laying-open No. 6-258640(1994) (corresponding to U.S. Pat. No. 5,452,385) discloses a display apparatus in which light propagating in the light guide is taken out by utilizing diffraction, and shuttering is effected by liquid crystal. However, in the display apparatus according to disclosed in such a document, since its diffraction grating is always in a diffraction state, diffraction efficiency cannot be varied. Therefore, there is a problem in that light always leaks from the light guide, resulting in a reduction of light utilization efficiency.
That is, there have been required for prior art optical display device and optical display apparatus to provide improved display characteristics such as increase in output light intensity, improvement of display contrast, and reduction of scattered light due to external light as well as ease of fabrication of large-area screen.
Objects of the present invention are as follows.
(1) Using a plate of a structure capable of guiding light and a refractive index-variable thin film, an object of the present invention is to provide an optical device for controlling retrieval of light and a display apparatus using the optical device.
(2) Using a plate of a structure capable of guiding light and a thin film capable of producing a scattering ability by an electric field, another object of the present invention is to provide an optical device for controlling retrieval of light and a display apparatus using the optical device.
(3) Using a plate of a structure capable of guiding light and a diffraction efficiency-variable thin film, a still further object of the present invention is to provide an optical device for controlling retrieval of light and a display apparatus using the optical device.
(4) Driving a plate of a structure capable of guiding light and a thin film by an electrode capable of making mirror reflection, a yet further object of the present invention is to provide an optical device for driving directly from the backside of the thin film and a display apparatus using the optical device.
(5) Using a polymer dispersed liquid crystal in an optical control layer, a yet further object of the present invention is to provide an optical device for controlling scattering or transmission or controlling diffraction efficiency and a display apparatus using the optical device.
(6) Using a reverse-mode polymer dispersed liquid crystal in an optical control layer, a yet further object of the present invention is to provide an optical device for making a gap between electrodes when making matrix driving by strip-shaped electrodes and preventing degradation of display image due to the gap of electrodes and a display apparatus using the optical device.
(7) Applying light from an end surface of a light guide and matrix driving a thin film, a yet further object of the present invention is to provide an optical device for achieving a display apparatus and a display apparatus using the optical device.
(8) Providing a reflection film, since light propagating in a light guide is reflected before reaching electrodes, a yet further object of the present invention is to provide an optical device for preventing light absorption by the electrodes and optical loss by electrode ends and a display apparatus using the optical device. In this case, the reflection film may be a dielectric multilayered film or a film lower in refractive index than said light guide.
(9) In particular, since, when using the dielectric multilayered film (or the film with a low refractive index), there is no electroconductivity, a yet further object of the present invention is to provide an optical device for reflecting without disarranging a driving electric field. Further, by a reflection characteristic having a directional selectivity, a yet further object of the present invention is to provide an optical device for reflecting only light being guided and a display apparatus using the optical device.
(10) When using a reflection film having a directional selectivity in reflection like a multilayered film by disposing a light-absorption film between electrodes and reflection film, a yet further object of the present invention is to provide an optical device for preventing visibility of the reflection film and electrodes from the side of viewing the device and a display apparatus using the optical device.
(11) A yet further object of the present invention is to provide an optical device for achieving a high-contrast, thin-structured, and lightweight large-screen display apparatus and a display apparatus using the optical device.
In a first aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a reflection plate provided on a lower surface of the optical control layer through a transparent electrode provided as a second electrode,
wherein the optical control layer changes in refractive index by an electric field applied by the first electrode and the second electrode, shows a refractive index substantially same as or greater than that of the plate-shaped light guide when no electric field is applied and shows a small refractive index as compared with the plate-shaped light guide when an electric field is applied, and
the reflection plate is made of a light transmissive material, a reflection surface of the reflection plate is angled at a predetermined angle with respect to a surface thereof on the optical control layer side, and a reflection film is formed on the reflection surface.
In a second aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a reflection plate made of a light transmissive plate provided on a lower surface of the optical control layer through a second electrode comprising the transparent electrode,
wherein the optical control layer is made of a reverse mode polymer dispersed liquid crystal changing in scattering degree by an electric field applied by the first electrode and the second electrode, which is constructed by dispersing a low molecular-weight liquid crystal in a liquid crystalline polymer, and the optical control layer becomes a uniform birefringent thin film when no electric field is applied and becomes a scattering state when an electric field is applied.
In a third aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a reflection plate made of a light transmissive plate provided on a lower surface of the optical control layer through a transparent electrode provided as a second electrode,
wherein the optical control layer changes in diffraction ability by an electric field applied by the first electrode and the second electrode.
In a fourth aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, a second electrode provided on a lower surface of the optical control layer, and a substrate provided on a lower surface of the second electrode,
wherein at least one of the first electrode and the second electrode has a periodic structure for inducing a fine periodic structure for light diffraction in the optical control layer, and
the optical control layer changes in refractive index or absorptivity or scattering degree by an electric field applied by the first electrode and the second electrode.
In a fifth aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide, periodic electrodes having periodic structures disposed in alternation and provided on a lower surface of the optical control layer for inducing a fine periodic structure for light diffraction in the optical control layer, and a substrate provided on a lower surface of the periodic electrodes disposed in alternation,
wherein the optical control layer changes in refractive index or absorptivity or scattering degree by an electric field applied by the periodic electrodes disposed in alternation.
In a sixth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device, wherein
the optical device has an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide, and a reflection plate made of a light transmissive plate provided on a lower surface of the optical control layer through a transparent electrode provided as a second electrode,
wherein the optical control layer is made of a reverse mode polymer dispersed liquid crystal changing in scattering degree by an electric field applied by the first electrode and the second electrode, which is constructed by dispersing a low molecular-weight liquid crystal in a liquid crystalline polymer, and the optical control layer becomes a uniform birefringent thin film when no electric field is applied and becomes a scattering state when an electric field is applied.
In a seventh aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device, wherein
the optical device has an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a second electrode provided as an electrode on a lower surface of the optical control layer for making mirror reflection of light,
wherein the optical control layer is made of a reverse mode polymer dispersed liquid crystal changing in scattering degree by an electric field applied by the first electrode and the second electrode, which is constructed by dispersing a low molecular-weight liquid crystal in a liquid crystalline polymer, and the optical control layer becomes a uniform birefringent thin film when no electric field is applied and becomes a scattering state when an electric field is applied.
In an eighth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device, wherein
the optical device has an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide, and a reflection plate made of a light transmissive plate provided on a lower surface of the optical control layer through a transparent electrode provided as a second electrode,
wherein the optical control layer changes in diffraction ability by an electric field applied by the first electrode and the second electrode.
In a ninth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device,
the optical device has an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a second electrode provided as an electrode on a lower surface of the optical control layer for making mirror reflection of light,
wherein the optical control layer changes in diffraction ability by an electric field applied by the first electrode and the second electrode.
In a tenth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device;
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, a periodic electrode provided as a second electrode having a periodic structure provided on a lower surface of the optical control layer for inducing a fine periodic structure for light diffraction in the optical control layer, and a substrate provided on a lower surface of the second electrode,
wherein at least one of the first electrode and the second electrode has a periodic structure for inducing a fine periodic structure for light diffraction in the optical control layer, and
the optical control layer changes in refractive index or absorptivity or scattering degree by an applied electric field, and is made of a reverse mode polymer dispersed liquid crystal changing in refractive index or absorptivity or scattering degree by an electric field applied by the first electrode and the second electrode, which is constructed by dispersing a low molecular-weight liquid crystal in a liquid crystalline polymer, and the optical control layer becomes a uniform birefringent thin film when no electric field is applied and becomes a scattering state when an electric field is applied.
In an eleventh aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device;
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, a second electrode provided on a lower surface of the optical control layer and comprising an electrode divided into a plurality of units, and a plurality of third electrodes corresponding one to one to each of the plurality of divided second electrodes and penetrating through the substrate,
wherein the optical control layer changes in refractive index or absorptivity or scattering degree or diffraction ability by an electric field applied by the first electrode and the second electrode,
each of the plurality of third electrodes has a first end part connecting to the second electrode and a second end part exposed to a surface opposite to the second electrode side of the substrate, and the respective electrodes are capable of being applied with a voltage from the substrate side discretely or dividedly in an optional number of groups.
In a twelfth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device;
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, a first stacked body integrated with an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a second stacked body integrated with each of substrate divided into a plurality of units,
wherein the second stacked body corresponds one to one to each of the second electrode divided into a plurality of units and a substrate provided on a lower surface of the second electrode and the plurality of divided second electrodes, has a plurality of third electrodes penetrating through the substrate, and arranged on a lower surface of the optical control layer,
the optical control layer changes in refractive index or absorptivity or scattering degree or diffraction ability by an electric field applied by the first electrode and the second electrode,
each of the plurality of third electrodes has a first end part connecting to the second electrode and a second end part exposed to a surface opposite to the second electrode side of the substrate, and the respective electrodes are capable of being applied with a voltage from the substrate side discretely or dividedly in an optional number of groups.
In a thirteenth aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, a reflection film provided on a lower surface of the optical control layer, a second electrode provided on a lower surface of the reflection film, and a substrate provided on a lower surface of the second electrode,
wherein the optical control layer changes in scattering degree or diffraction efficiency by an electric field applied by the first electrode and the second electrode,
In a fourteenth aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, a reflection film provided on a lower surface of the optical control layer, a second electrode provided on a lower surface of the reflection film, and a substrate provided on a lower surface of the second electrode,
wherein at least one of the first electrode and the second electrode has a periodic structure for inducing a fine periodic structure for light diffraction in the optical control layer, and
the optical control layer changes in refractive index or scattering degree or absorbance by an electric field applied by the first electrode and the second electrode.
In a fifteenth aspect of the present invention, there is provided an optical device comprising a light transmissive plate-shaped light guide for guiding light incident from an end surface, an optical control layer provided on a lower surface of the plate-shaped light guide, a reflection film provided on a lower surface of the optical control layer, an electrode comprising periodic electrodes having periodic structures disposed in alternation and provided on a lower surface of the reflection film for inducing a fine periodic structure for light diffraction in the optical control layer, and a substrate provided on a lower surface of the electrode having periodic electrodes disposed in alternation.
wherein the optical control layer changes in refractive index or scattering degree or absorbance by an electric field applied by the electrode having periodic electrodes disposed in alternation.
In a sixteenth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device,
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the light guide through a transparent electrode provided as a first electrode, a reflection film provided on a lower surface of the optical control layer, a second electrode provided on a lower surface of the reflection film, and a substrate provided on a lower surface of the second electrode,
wherein the optical control layer changes in scattering degree or diffraction efficiency by an electric field applied by the first electrode and the second electrode.
In a seventeenth aspect of the present invention, there is provided a display apparatus comprising an optical device and a illumination means for applying light to the optical device,
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the light guide through a transparent electrode provided as a first electrode, a reflection film provided on a lower surface of the optical control layer, a second electrode provided on a lower surface of the reflection film, and a substrate provided on a lower surface of the second electrode,
wherein at least one of the first electrode and the second electrode has a periodic structure for inducing a fine periodic structure for light diffraction in the optical control layer, and
the optical control layer changes in refractive index or scattering degree or absorbance by an electric field applied by the first electrode and the second electrode.
In an eighteenth aspect of the present invention, there is provided a display apparatus comprising: an optical device, a illumination means for applying light to the optical device,
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, a reflection film provided on a lower surface of the optical control layer, a second electrode comprising an electrode divided into a plurality of units provided on a lower surface of the reflection film, a substrate provided on a lower surface of the second electrode, and a plurality of third electrodes corresponding one to one to each of the plurality of second electrode, penetrating through the substrate,
wherein the optical control layer changes in refractive index or absorptivity or scattering degree or diffraction ability by an electric field applied by the first electrode and the second electrode,
each of the plurality of third electrodes has a first end part connecting to the second electrode and a second end part exposed to a surface opposite to the second electrode side of the substrate, and the respective electrodes are capable of being applied with a voltage from the substrate side discretely or dividedly in an optional number of groups.
In a nineteenth aspect of the present invention, there is provided a display apparatus comprising: an optical device, a illumination means for applying light to the optical device,
the optical device having an end surface for incident light from the illumination means, a light transmissive plate-shaped light guide for guiding incident light, a first stacked body integrated with an optical control layer provided on a lower surface of the plate-shaped light guide through a transparent electrode provided as a first electrode, and a second stacked body integrated with each of substrate divided into a plurality of units,
wherein the second stacked body has a reflection film, a second electrode divided into a plurality of units provided on a lower surface of the reflection film, a substrate provided on a lower surface of the plurality of divided second electrodes, and a plurality of third electrodes corresponding one to one to each of the plurality of divided second electrodes, penetrating through the substrate, and arranged on a lower surface of the optical control layer,
the optical control layer changes in refractive index or absorptivity or scattering degree or diffraction ability by an electric field applied by the first electrode and the second electrode,
each of the plurality of third electrodes has a first end part connecting to the second electrode and a second end part exposed to a surface opposite to the second electrode side of the substrate, and the respective electrodes are capable of being applied with a voltage from the substrate side discretely or dividedly in an optional number of groups.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings.